PLLs are subject to undesired frequency deviation effects due to many causes. For example, Cartesian and polar RF transmitters are subject to a local oscillator pulling effect which causes distortion of the transmitted signal. Local oscillator pulling is essentially re-modulation of the local oscillator frequency that is for example caused by radiated or conducted interference induced by the varying amplitude of the strong signal output by the transmitter or the power amplifier. Oscillator pulling is not only restricted to pulling induced by the transmit signal, but it can be caused by arbitrary aggressors. For instance, due to the crosstalk through digital switching circuits the oscillator can experience pulling generating undesired spurious sidebands.